Antistatic photographic film



United States Patent 3,547,643 ANTISTATIC PHOTOGRAPHIC FILM Karl Pechmann, Binghamton, N.Y., assignor to GAF Corporation, New York, N .Y., a corporation of Delaware No Drawing. Filed July 23, 1968, Ser. No. 746,733

Int. Cl. G03c 1/82 US. Cl. 96-87 Claims ABSTRACT OF THE DISCLOSURE An antistatic photographic film is provided containing in at least one layer an antistatic agent therefor, an ampholytic compound of the formula:

S or wherein R is a long chain alkyl radical from about 8 to about 18 carbon atoms.

The present invention relates to antistatic photographic elements, e.g., photographic film; more particularly, the present invention relates to a photographic film containing in at least one layer thereof certain ampholytic compounds as antistatic agents.

The accumulation of electrical charges on the photographic films and similar photographic elements has been the cause of considerable difficulty in the past. Thus, for example, considerable difliculty has been encountered both during the manufacture and use of photographic films due to the static electrical charges that are produced by friction of the film from rollers or other parts of the machine through which the film passes; by splitting or unwinding the film; by contact with dissimilar surfaces; by handling the film; or by other causes well known in the field of producing photographic films.

In addition, such discharges can also occur in films such as motion picture film when it is rapidly transported through the camera. Therefore, it is quite clear that the production of such electrical charges can occur not only during the manufacture of the film but also in the use of the same. When these static charges reach a sufficiently high intensity at discharge can occur resulting in static lines on the sensitized film, the presence of such static lines rendering the product unsuitable. Thus the accumulation of such static charges generally manifest itself in the formation of irregular streaks or patterns or lines in the film caused by lightning-like exposures at such portions. Inasmuch as it is very difficult to determine Whether the photographic film has been damaged to any extent by the accumulation of static charges prior to exposure and processing of the same, it has been found an extremely desirable object to protect the film and similar photographic elements from this unwanted accumulation of static electrical charges.

Previous attempts to overcome the unwanted static accumulation in photographic films and similar photographic elements have for the most part followed the concept of utilizing conducting or hygroscopic materials on the surface of the film in order to increase its electrical conductivity and prevent the formation or buildup of static electrical charges. However, such methods have not proven wholly satisfactory, especially under conditions of low humidity where the static problem is most acute.

Thus, for example, it has been previously proposed to incorporate certain ionic organic materials including water soluble materials as described in Morey and White,

'ice

US. Pat. 2,639,234. Similarly, the use of water soluble inorganic acid salts has been proposed. Also, various proposals have included the employment of materials which, as noted previously, absorb water and therefore provide a conductive surface upon the photographic film. Again, however, such previous attempts to eliminate the problem of accumulation of static charges on photographic films and similar photographic elements have for the most part proved unsatisfactory, especially in connection with the newer high speed emulsions and with the different film types now being manufactured.

In addition, a number of the materials which have been previously proposed as antistatic agents for use in various systems have been found incompatible with the different ingredients used in the photographic film, and some have even been found to have an adverse effect on the photographic emulsion. Accordingly, it is still the desire of the industry to provide an efficient, antistatic agent which, when incorporated into a photographic film or similar photographic element, will provide a photographic element product of approved antistatic properties and one having a lessened tendency to accumulate static electrical charges.

Thus in accordance with the present invention it has been discovered that the static susceptibility of photographic films can be minimized by adding to one or more layers of such photographic film an antistatic amount of certain ampholytic compounds. Accordingly, it is a principal object of the present invention to provide an antistatic photographic film or similar photographic element which by virtue of the antistatic agent employed therein eliminates the deficiencies and disadvantages of'the prior art.

A further object of the present invention is to provide an antistatic photographic film or similar photographic element containing in one or more layers thereof an antistatic amount of an ampholytic compound.

A still further object of the present invention comprises a photographic film or similar photographic element containing in one or more layers thereof an antistatic amount of an ampholyte of the formula:

wherein R is a long chain alkyl radical from 8 to about 18 carbon atoms.

Still further objects and advantages of the novel product of the present invention become more apparent from the following more detailed description thereof.

The above objects and advantages of the novel product of the present invention are realized by the provision of a photographic film or similar photographic element wherein an antistatic amount of an ampholyte compound of the formula:

wherein R is a long chain alkyl group of about 8 to 18 carbon atoms is incorporated into one or more layers thereof.

As noted from the above general formula of the ampholytic compounds employed in accordance with the present invention, the radical R comprises a long chain alkyl group, i.e., a branched or straight chain alkyl group,

Patented Dec. 15, 1970' generally having from about 8 to 18 carbon atoms.

Exemplary groups, for example, comprise:

n-octane n-tetradecane n-nonane n-pentadecane n-decane n-hexadecane n-undecane n-heptadecane n-dodecane n-octodecane, etc. n-tridecane as well as the branch chain isomers of such straight chain alkyl groups including, for, example: 2,2,4-trimethyl pentane, 4-methyl-3,3-diethyl-5-isopropyl octane, 2,2,4- trimethyl heptane, 2,3-diethyl pentane, etc.

Accordingly, exemplary ampholytic compounds found within the above general formula include the following:

n-octyl amino sulfonate n-nonyl amino sulfonate n-dodecyl amino sulfonate n-tridecyl amino sulfonate n-tetradecyl amino sulfonate n-hexadecyl amino sulfonate n-octadecyl amino sulfonate iso-octyl amino sulfonate, etc.

Such higher alkyl amino sulphate ampholytic compounds employed as antistatic agents in accordance with the present invention are prepared by conventional methods known in the art. Thus, for example, they can be advantageously prepared by reacting a long chain alkyl halide ammonium halide, e.g., n-octylbromide ammoniumbromide with an alkali sulfide, e.g., sodium sulfide pholytic compounds containing a mixture of materials of diiferent alkyl chains comprising the residue of fatty acid mixtures. Such commercially available ampholytic compounds suitably and preferably employed in accordance with the present invention comprise, for example, the Varions sold by Varney Chemical Corporation. Suitable materials of this nature include for example, the Varion l0l7coco amino sulfonate and Varion l084tallow amino sulfonate.

Again, such ampholytic compounds falling within the above noted generic formula and comprising a mixture of such compounds are preferably employed in accordance with the present invention.

As noted from the above, the ampholytic agents employed in accordance with the present invention are such as to contain both an acidic and basic group in the single molecule. Thus, unlike other classes of surface active agents, the ampholytic compounds change their ionic character with changes in acidity. Accordingly, they are predominantly cationic in behavior at low pH levels, and predominantly anionic in behavior at high pH levels. At some intermediate, called the isoelectric point, the positive and negative changes balance and a so-called Zwitterion is formed, as illustrated in the above general formula, such Zwitterion being electrically neutral and suitably regarded as non-ionic in behavior.

As indicated above, the ampholytic compounds antistatic agents in accordance with the present invention are generally incorporated in one or more layers of the photographic film or similar photographic elements. Thus in accordance with one embodiment of the present invention the ampholytic, antistatic agents of the present invention are advantageously incorporated in the lightsensitive emulsion layer of the photographic film, e.g., the silver halide emulsion. While this is one method of providing the necessary antistatic characteristics to the photographic film, it is also possible, as with another embodiment of the present invention, to include the antistatic agent within a separate surface layer over the emulsion layer of the photographic film. Generally, such separate surface layer comprises a gelatin or gelatin substitute layer, e.g., hydrophilic colloid, containing an antistatic amount of the ampholytic compounds employed in accordance with the present invention. Similarly, while the antistatic agent can be employed in a surface layer on one side of the photographic film or similar element, it is likewise possible to include the antistatic agents of the present invention in surface layers on both sides of the photographic film support, or between the film support and the photographic emulsion layer so as to provide the necessary antistatic characteristics and prevent the curling of the photographic product.

In addition, the antistatic agents for photographic films employed in accordance with the present invention can be utilized insolvent solutions, i.e., aqueous or organic solvent solutions as an antistatic backwash for application to the photographic film support such as a conventional cellulose acetate or a polyester film support, prior to the application of the light sensitive emulsion on the other side of the film. This type of application of the antistatic agent to the film support from such a solvent solution on the opposite side of the photographic emulsion is especially applicable for a cine film. Likewise, the antistatic agents for photographic films employed in accordance with the present invention can be added to a conventional subbing solution used to provide better adhesion between the photographic film support and the light sensitive emulsion, e.g., silver halide emulsion or the non-curl layer. From the above, therefore, it can be seen that the antistatic agents employed in accordance with the present invention, i.e., the ampholytic compounds of the general formula noted above, can be utilized in any and all of the layers conventionally employed in the production of a photographic film. Similarly, it is also apparent that the antistatic agents employed in accordance with the present invention can be suitably employed both in color films as well as black and white films and can be advantageously employed as coatings on paper or plastic coated paper as well as conventional plastic film base materials.

It is a further feature of the present invention that when the ampholytic antistatic agents are added to a photographic emulsion, e.g., a light sensitive silver halide emulsion, they facilitate the spreading of a gelatin or similar layer over the wet chilled emulsion when both layers are applied in the same coating pass. Thus, for example, the addition of only about 5 cc. of a 10% solution of the ampholytic agents, e.g., coco amino sulfonate or tallow amino sulfonate to one kilogram of silver halide emulsion increases the coating speed at which a thin gelatin surface solution may be applied over a wet chilled silver halide emulsion layer from less than fifty feet per minute to one hundred feet per minute. This, of course, is a further advantageous property associated with the novel photographic films and similar elements of the present invention.

While, as stated previously, the ampholytic compounds employed in accordance with present invention need only be employed in those amounts necessary to provide the desired antistatic characteristics to the photographic film or similar photographic element. When employed as a component of the silver halide emulsion, however, such antistatic agents are generally employed in the amount of from about 0.1 to about 10.0 percent by weight based on the total weight of the emulsion, a range of from 0.5 to 2.5 percent being preferred. Similarly, when employed in a gelatin or similar hygroscopic colloid surface layer of the photographic film or similar photographic element the antistatic agents are generally employed in an amount of from about 1 to 10 grams per liter of 2 percent gelatin solution. The concentration in gelatin non-curl layers ranges from 2 to 10 percent by Weight, based on the weight of dry gelatin used in the preparation of the layer.

EXAMPLE I On both sides of a cellulose acetate support were coated a layer of silver halide X-ray emulsion containing the usual adjuvants and over the emulsion layer an antiabrasion layer of 2% gelatin containing a hardener for the gelatin, a matte agent and a spreading agent.

A second coating was made but to the gelatin solution before coating was added a solution in water of coco amino sulfonate-Varion 1017, at a concentration of 2400 cc. per 1 kilogram of dry gelatin. This gave a concentration of 24% of the antistatic agent per weight of dry gelatin.

The coatings were cut into strips, 1 inches wide and 10 inches long. After conditioning at a relative humidity of 20%, ten strips of each coating were rubbed in total darkness with a nylon pad so as to generate static electricity in the film. The film strips were then processed together in the usual manner which included development, fixing, washing and drying. They were then examined for static discharge marks which can readily be recognized by the black streaks, specks, lines or various other patterns in the otherwise clear emulsion.

Of the 10 strips containing the antistatic agent, none exhibited static markings; all of the control strips showed static markings varying from light to medium in severity.

EXAMPLE II A set of eight strips each from the coatings of Example I were subjected to a similar test in which after conditioning at a relative humidity of 20% the strips were rubbed with the fingers instead of with nylon. The con trol strips all exhibited medium to heavy static markings; four of the strips from the coating containing the antistatic agent in the surface layer had no static; four had a few light marks.

Surface resistivity of the control coating was 200x10 megohms; of the one with antistatic agent, 60 10 megohms.

EXAMPLE IH Coatings were made in a similar manner to Example I, but this time one contained a 10% solution of tallow amino sulfonate-Varion 1084 at a concentration of 2000 cc. per 1 kilogram of gelatin in the surface layers. On the nylon rub test, two coatings had no markings and eight had very light markings, compared with nine medium and one light for the control. On the finger rub test, the evaluation was four strips with light and four with medium markings, compared to three medium and five heavy for the control. Again a significant reduction in the level of static markings was found.

EXAMPLE IV A coating was made on polyester filmbase of a gelatin non-curl layer containing antihalation dyes, a gelatin hardener and a spreading agent. On the opposite side of the support was coated a layer of silver halide emulsion containing the usual adjuvants, suitable for a black and white portrait film.

A second coating was made containing 750 cc. of 10% Varion 1017 per kilogram of gelatin in the non-curl layer. The coatings were slit and evaluated as described in Example I, for nylon rub static, by rubbing the non-curl layer. All of the strips from the control coating exhibited static markings varying in degree from medium to heavy; none of the strips from the coating with the antistatic agent showed such markings.

6 EXAMPLE v A second set of strips from the coatings of Example IV were submitted to a finger rub test. A definite reduction in static marks was observed with the coating containing the coco amino sulfonate antistatic agent.

EXAMPLE VI Example IV was repeated, but tallow amino sulfonate at a concentration of 450 cc. per kilogram gelation was used in place of the coco amino sulfonate. The results of the nylon rub test were the same as in Example IV.

A reduction in finger rub static was observed but it was less than with the 750 cc. of the coco amino sulfonate EXAMPLE VII Example IV was again repeated except that the antistatic agent was replaced by a substantially equal amount of the following materials.

(a) n-octyl amino sulfonate (b) iso-octyl amino sulfonate (c) dodecyl amino sulfonate (d) tetradecyl amino sulfonate (e) octadecyl amino sulfonate In all cases, substantially equivalent results are obtained.

While the present invention has been described primarily with respect to foregoing specific examples it is to be understood that the present invention is in no way to be deemed as limited thereto but must be construed as broadly as all or any equivalents thereof.

I claim:

1. A photographic film comprising a film support having thereon a light sensitive silver halide emulsion layer containing, in an amount effective to impart antistatic properties to said film, at least one ampholytic compound of the formula:

wherein R is an alkyl group of about 8 to 18 carbon atoms.

2. The photographic film of claim 1 wherein said ampholytic compound comprises tallow amino sulfonate.

3. The photographic film of claim 1 wherein said ampholytic compound comprises coco amino sulfonate.

4. A photographic film comprising a film support, a light sensitive silver halide emulsion layer and a gelatin layer, said gelation layer containing, in an amount effective to impart antistatic properties to said film, at least one ampholytic compound of the formula:

\NH3+ wherein R is an alkyl group of about 8 to 18 carbon atoms.

5. The photographic film of claim 4 wherein said ampholytic compound is employed in an amount of 1 to 10 percent by weight based on the Weight of the gelatin.

6. The photographic film of claim 4 wherein said ampholytic compound comprises tallow amino sulfonate.

7. The photographic film of claim 4 wherein said ampholytic compound comprises coco amino sulfonate.

8. A method of imparting antistatic properties to a photographic film which comprises applying thereto, in an amount effective to impart said antistatic properties, at least one ampholytic compound of the formula:

8 wherein R is an alkyl group of about 8 to 18 carbon References Cited atoms. I E

9. The method of claim 8 wherein said ampholytic com- UN T D STATES PATENTS pound is applied to one side of a film support from a solu- 2,139,778 12/1938 Slack et 96114'2 X tion as a photographic backwash prior to application of 5 fi z et i l ht 't' 'l h 1d 1 '0 l t th other o or a 1g we S1 Var a1 6 emu S1 n ayer 0 e 3,441,413 4/1969 Nishio et a1 96114.5 X

side of said film support.

10. The method of claim 8 wherein said ampholytic compound is applied from a solution to a film support RICHARD SMITH Pnmary Exammer as subbing layer to provide adhesion between said film 10 U S C} XR support and a subsequently applied light sensitive silver film halide emulsion layer. 96-1142, 114.5, 84, 85 

